Wireless communication with interference mitigation

ABSTRACT

In one implementation, a wireless communication terminal includes a primary antenna array and a first controller configured to steer a main beam of the primary antenna array in a desired direction. The wireless communication terminal also includes an auxiliary antenna array and a second controller configured to control complex weights to be applied by at least some antenna elements of the auxiliary antenna array to corresponding variants of a second signal received by the at least some auxiliary antenna elements. Furthermore, the wireless communication terminal includes at least one signal combiner configured to combine variants of the second signal received from auxiliary antenna elements into an interfering signal that models interference from a co-located wireless communication terminal and subtract the interfering signal from variants of the first signal received from antenna elements of the principal antenna array to produce an interference mitigated signal.

PRIORITY

This application is a continuation under 35 U.S.C. §120 of U.S. patentapplication Ser. No. 14/484,895 filed Sep. 12, 2014, which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosure relates generally to wireless communication, and morespecifically to wireless communication with interference mitigation.

SUMMARY

According to one implementation of the disclosure, a wirelesscommunication terminal includes a primary antenna array and a firstcontroller configured to steer a main beam of the primary antenna arrayin a desired direction. The wireless communication terminal alsoincludes an auxiliary antenna array and a second controller configuredto control complex weights to be applied by at least some antennaelements of the auxiliary antenna array to corresponding variants of asecond signal received by the at least some auxiliary antenna elements.Furthermore, the wireless communication terminal includes at least onesignal combiner configured to combine variants of the second signalreceived from auxiliary antenna elements into an interfering signal thatmodels interference from a co-located wireless communication terminaland subtract the interfering signal from variants of the first signalreceived from antenna elements of the principal antenna array to producean interference mitigated signal.

According to another implementation of the disclosure, a main signal isreceived with a primary antenna array. The main signal includes noisefrom a proximally located wireless communication terminal received inone or more side lobes of the primary antenna array. Variants of asecondary signal are received with corresponding antenna elements of anauxiliary antenna array. Complex weights to be applied by individualantenna elements of the auxiliary antenna array to the correspondingvariants of the secondary signal received by the individual antennaelements are set based on a direction of a main beam of the primaryantenna array. The complex weights are applied to the correspondingvariants of the secondary signal received by the individual antennaelements to shift (e.g., in amplitude and/or phase) the variants of thesecondary signal received by the individual antenna elements. Theshifted variants of the secondary signal then are combined into aninterfering signal to model the noise from the proximally locatedwireless communication terminal received in the one or more side lobesof the primary antenna array and the interfering signal is subtractedfrom the main signal to produce an interference mitigated signal.

In yet another implementation of the disclosure, a satellitecommunication terminal includes a primary antenna array, an auxiliaryantenna array, first and second controllers, and at least one signalcombiner. The primary antenna array includes a first number of primaryantenna elements. Individual ones of the primary antenna elements areconfigured to receive variants of a first signal. Similarly, theauxiliary antenna array includes a second number of auxiliary antennaelements and individual ones of the auxiliary antenna elements areconfigured to receive variants of a second signal. The first controlleris configured to steer a main beam of the primary antenna array in adesired direction to receive a desired signal from a satellite orbitingthe earth. The second controller is configured to control complexweights to be applied by at least some of the auxiliary antenna elementsto the corresponding variants of the second signal received by the atleast some auxiliary antenna elements. The at least one signal combineris configured to combine variants of the second signal received fromauxiliary antenna elements into an interfering signal that models asignal transmitted by a co-located satellite communication terminalreceived in one or more side lobes of the satellite communicationterminal and subtract the interfering signal from variants of the firstsignal received from principal antenna elements to produce aninterference mitigated version of the desired signal.

Other features of the present disclosure will be apparent in view of thefollowing detailed description of the disclosure and the accompanyingdrawings. Implementations described herein, including theabove-described implementations, may include a method or process, asystem, or computer-readable program code embodied on computer-readablemedia.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referencenow is made to the following description taken in connection with theaccompanying drawings.

FIG. 1 is a high level block diagram of a system for wirelesscommunication with interference mitigation in accordance with anon-limiting implementation of the present disclosure.

FIG. 2 is a flow chart of a method for wireless communication withinterference mitigation in accordance with a non-limiting implementationof the present disclosure.

FIG. 3 is a block diagram of a system for wireless communicationconfigured to provide interference mitigation.

DETAILED DESCRIPTION

Satellite communication systems may enable wireless voice and datacommunications around the world. In some cases, satellite communicationsystems enable communication in regions where other wirelesscommunication systems may not be available. For example, some wirelesscommunication systems may require terrestrial infrastructure (e.g., acell tower, a base station, etc.). It may not be possible to communicateusing these systems in regions where the necessary terrestrialinfrastructure does not exist or cannot be accessed. However, satellitecommunication systems still may be capable of communicating in suchregions. Examples of these regions include the oceans, the airways, thepolar regions, and developing and/or underdeveloped nations. Frequently,multiple satellite communication systems may be co-located (e.g., withina fixed relative area). For example, a ship equipped with two or moresatellite communication systems may have only a small deck area suitablefor installing the antennae for the satellite communication systems and,consequently, the antennae for the satellite communication systems maybe forced to be installed in close physical proximity to one another(e.g., within a few feet or yards of one another on the deck).Similarly, an aircraft equipped with two or more satellite communicationsystems may have limited external area suitable for mounting theantennae for the satellite communications systems. As a result, theantennae for the satellite communication systems may be mounted in closephysical proximity to one another.

In some cases, two or more co-located satellite communication systemsmay use similar, adjacent, neighboring, and/or overlapping frequencies(e.g., for transmit and/or receive functions of satellitecommunication). As a result, an output signal transmitted by a firstsatellite communication system may interfere with the ability of asecond, co-located satellite communication system to receive an inputsignal, and vice versa, particularly if the power of the output signalis significantly greater than the power of the input signal. Forexample, if the first satellite communication system transmits arelatively high-power output signal in a frequency band that isimmediately adjacent to the frequency band in which the second satellitecommunication system receives a relatively low-power input signal,components of the relatively high-power output signal may spill overinto the frequency band in which the second satellite communicationsystem receives the low-power input signal and, particularly due to thepower difference between the two signals, cause interference with therelatively low-power input signal, thereby degrading the performance ofthe second satellite communication system. Additionally oralternatively, the presence of the relatively high-power output signalmay cause reciprocal mixing in the receiver of the second satellitecommunication system also resulting in degradation of the secondsatellite communication system's ability to receive the relativelylow-power input signal. Local oscillators with relatively goodphase-noise performance may be employed to mitigate the effect of suchreciprocal mixing, but such high performance oscillators may berelatively expensive. Application of the interference mitigationtechniques described herein may enable the use of potentially cheaperlocal oscillators with worse phase-noise performance while stillproviding protection against reciprocal mixing.

In one specific example, an IRIDIUM® satellite terminal that uses L bandfrequencies between 1616 and 1626.5 megahertz (“MHz”) to communicatewith IRIDIUM® satellites may be co-located (e.g., on a ship or aircraft)with an INMARSAT® satellite terminal that uses L band frequenciesbetween 1525 and 1646.5 MHz to communicate with one or more INMARSAT®satellites. Consequently, transmissions to/from the INMARSAT® satelliteterminal may pose the potential for interference with transmissionsto/from the IRIDIUM® satellite terminal and vice versa. For example, theINMARSAT® satellite terminal may transmit communications in a frequencyband that is adjacent to a frequency band in which the IRIDIUM®satellite terminal receives transmissions from IRIDIUM® satellites.Accordingly, outbound transmissions from the INMARSAT® satelliteterminal may pose the potential to interfere with transmissions receivedby the IRIDIUM® satellite terminal and/or cause reciprocal mixing in theIRIDIUM® satellite terminal resulting in signal degradation,particularly given the relatively high power of output transmissionsfrom the INMARSAT® satellite terminal required to reach an INMARSAT®satellite and the relatively low power of transmissions received by theIRIDIUM® satellite terminal from an IRIDIUM® satellite. For example, thepower ratio of transmissions output by the INMARSAT® satellite terminalto transmissions received by the IRIDIUM® satellite terminal may be onthe order of +100 dB or more.

A satellite communication terminal may be configured to mitigate theeffects of interference from one or more other satellite communicationterminals in the event that the satellite communication terminal isco-located with one or more other satellite communications terminals,for example that use similar, adjacent, neighboring, and/or overlappingfrequencies. For instance, a satellite communication terminal configuredto receive a signal from one or more satellites even when co-locatedwith another satellite communication terminal that transmits an outputsignal in a similar, adjacent, neighboring, and/or overlapping frequencyband may employ beam steering (e.g., using complex weights, phaseshifters, etc.) to steer the main beam of the satellite communicationterminal's antenna toward the signal to be received (and, in some cases)away from the interfering signal output by the co-located satellitecommunication terminal. However, in some cases (e.g., if the power ofthe interfering signal is significantly greater than the power of thesignal to be received), such beam steering alone may not effectivelymitigate the interference caused by the signal transmitted by theco-located satellite communication terminal.

Additionally or alternatively, the satellite communication terminal mayemploy frequency domain filtering techniques (e.g., band pass filtering,for instance, using a surface acoustic wave (“SAW”) filter) to mitigateinterference caused by the signal transmitted by the co-locatedsatellite communication terminal. However, in some cases (e.g., if theinterfering signal is in a similar, adjacent, neighboring, and/oroverlapping frequency band and particularly if the power of theinterfering signal is significantly greater than the power of the signalto be received), such frequency domain filtering techniques alone maynot effectively mitigate the interference caused by the signaltransmitted by the co-located satellite communication terminal.

As described herein, implementations of the present disclosure mayprovide a satellite communication system configured to mitigate theeffects of interference from one or more other co-located satellitecommunication systems. For example, implementations of the presentdisclosure may utilize a combination of a main antenna or antenna arrayand an auxiliary antenna or antenna array to receive an interferingsignal from a co-located satellite communication system and subtract theinterfering signal from the signal received by the main antenna tomitigate the interference caused by the interfering signal to thedesired signal. In certain implementations, spatial filtering techniques(e.g., shaping an antenna's transmit/receive response) may be employedto mitigate interference caused by the co-located satellitecommunication system. For example, the primary antenna may be asteerable antenna (e.g., a switched beam antenna or an adaptive arrayantenna) configured to steer a beam (e.g., a main beam) of the primaryantenna in a direction perceived as advantageous for receiving thedesired satellite signal and the auxiliary antenna may be configured toreceive the interfering signal from the co-located satellitecommunication system such that the interfering signal received by theauxiliary antenna can be subtracted from the signal received by theprimary antenna to mitigate the effects of the interfering signalreceived by the primary antenna.

In certain implementations, the gain of the auxiliary antenna may berelatively low compared to the gain of the primary antenna. Furthermore,complex weights may be applied to the signal received by the auxiliaryantenna to shift the amplitude and/or phase of the signal received bythe auxiliary antenna in an effort to optimize the cancellation of theinterfering signal from the co-located satellite communication system.

With reference to FIG. 1, a high level block diagram of a system 100 forwireless communication is illustrated in accordance with a non-limitingimplementation of the present disclosure. System 100 includes satellites10 and 20, wireless communication terminal 30 for receiving a signalfrom satellite 20, and interfering wireless communication terminal 50for transmitting a signal to satellite 10. Wireless communicationterminal 30 includes a primary antenna array 32, an auxiliary antennaarray 34, a modem 36, a power receiver 38, a Beam Steering Controller(“BSC”) 40, and an Interference Canceller Controller (“ICC”) 42. Primaryarray 32 has one or more antenna elements 43 a-c, each of which includesa corresponding transmit/receive module 44 a-c. Auxiliary array 34 hasone or more antenna elements 45 a-c, each of which includes acorresponding receive module 46 a-c. For example, primary antenna array32 may have 12 antenna elements, and auxiliary antenna array 34 may have3 antenna elements. Primary array 34 may transmit and/or receive signalsto satellite 20.

Interfering wireless communication terminal 50 includes one or moreantenna elements 52. Antenna elements 52 communicate with satellite 10.When interfering wireless communication terminal 50 is transmitting tosatellite 10, antenna 52 may send a relatively high power transmissionsignal (particularly when compared to the power of the signal thatwireless communication terminal 30 receives from satellite 20) frominterfering wireless communication terminal 50 to satellite 10. Therelatively high power transmission signal sent by interfering wirelesscommunication terminal 50 may be in a similar, adjacent, neighboringand/or overlapping frequency band to a frequency band in which wirelesscommunication terminal 30 is configured to receive signals fromsatellite 20. Furthermore, wireless communication terminal 30 may belocated in close proximity (e.g., less than 5 feet, between 5 and 15feet, between 15-50 feet, etc.) to interfering wireless communicationterminal 50. Thus, the relatively high power transmission signal sent byinterfering wireless communication terminal 50 may interfere with theability of wireless communication terminal 30 to receive the relativelylow power signal from satellite 20.

The BSC 40 may be configured to steer a main beam of primary antennaarray 32 in a desired direction to facilitate the transmission ofsignals to and/or the reception of signals from satellite 20. Forexample, BSC 40 may control complex weights applied by transmit/receivemodules 44 a-44 c to signals transmitted/received by antenna elements 43a-43 c to steer a main beam of primary antenna array 32 in the desireddirection. However, even with a main beam of primary antenna array 32positioned to facilitate the reception of the signal from satellite 20,the signal transmitted by interfering wireless communication terminal 50still may interfere with the ability of wireless communication terminal30 to receive the signal from satellite 20. For example, even if a mainbeam of primary antenna array 32 is steered in the direction ofsatellite 20 (and/or away from interfering wireless communicationterminal 50), the signal transmitted by interfering wirelesscommunication terminal 50 still may be received in the side lobe(s) ofprimary antenna array 32.

Therefore, auxiliary antenna array 34 may be used to sample the signaltransmitted by interfering wireless communication terminal 50 so thatthe sampled interfering signal may be subtracted from the signalreceived by primary antenna array 32 to produce an interferencemitigated signal that thereafter is provided to modem 36. In certainimplementations, a main beam of auxiliary antenna array 34 may besteered in a particular direction to facilitate reception of theinterfering signal from interfering wireless communication terminal 50.In certain implementations, power receiver 38 may measure the power inthe interference mitigated signal, and ICC 42 may control complexweights applied by receive modules 46 a-46 c to the signals received byantenna elements 45 a-45 c in an effort to minimize the power in theinterference mitigated signal. Furthermore, in certain implementations,the above-described signal processing may be performed at radiofrequencies (“RF”) (e.g., before the received signal is converted to anintermediate frequency, baseband, etc.).

With reference to FIG. 2, a flow chart 200 of a method for wirelesscommunication with interference mitigation is illustrated in accordancewith a non-limiting implementation of the present disclosure. The methodillustrated in flow chart 200 may be performed by the wirelesscommunication terminal 30 illustrated in FIG. 1. At step 210, a mainbeam of a primary antenna array is steered to a desired direction. Forexample, a desired signal to be received may be transmitted by asatellite orbiting the earth, and a main beam of the primary antennaarray may be steered in a direction favorable for receiving the desiredsignal. In some implementations, a main beam of the antenna array may besteered in the desired direction by defining complex weights to beapplied to the signals received by the antenna elements of the primaryantenna array. At step 220, complex weights to be applied by theauxiliary antenna array are set based on the direction of the main beamof the primary antenna array. As described in greater detail below, insome implementations, the complex weights to be applied may becalculated substantially in real-time as the main beam of the primaryantenna is steered, while, in other implementations, the complex weightsto be applied may have been predetermined (e.g., during a calibrationprocess) for each of a number of different possible directions in whichthe main beam of the primary antenna may be steered.

At step 230, a main signal is received by the primary antenna array. Themain signal may include noise from a signal transmitted by anothernearby wireless communication terminal. For example, the signaltransmitted by the nearby wireless communication terminal may bereceived in one or more side lobes of the primary antenna array. In somecases, the power of the signal transmitted by the nearby wirelesscommunication terminal may be significantly greater than the power ofthe signal desired to be received (e.g. +100 dB).

In parallel with receiving the main signal, at step 240, a secondarysignal is received with the auxiliary antenna array. The secondarysignal received by the auxiliary antenna array may include the signaltransmitted by the nearby wireless communication terminal. As such, theauxiliary antenna array may be said to sample the signal transmitted bythe nearby wireless communication terminal. In some implementations, theindividual antenna elements of the auxiliary antenna array may receivevariants (e.g., time- and/or phase-shifted variants) of the secondsignal. At step 250, the antenna elements of the auxiliary antenna arrayapply the previously set complex weights to the variants of thesecondary signal they received, thereby generating shifted (e.g.phase-shifted) variants of the secondary signal. At step 260, theshifted variants of the secondary signal are combined into aninterfering signal (e.g., that models the signal transmitted by thenearby wireless communication terminal).

At step 270, the interfering signal is subtracted from the main signal.Subtracting the interfering signal from the main signal may result innoise (e.g., the signal transmitted by the nearby wireless communicationterminal) being canceled or reduced from the main signal to enablefurther processing of a desired signal included within the main signal.The resulting signal, therefore, may be referred to as an interferencemitigated signal.

In some implementations, the power in the interference mitigated signalmay be monitored, and the weights to be applied by the antenna elementsof the auxiliary antenna array may be calculated to minimize (or atleast reduce) the power in the interference mitigated signal. Forexample, in some particular implementations, a calibration process maybe performed upon installation of the device and/or at intervalsthereafter to determine appropriate complex weights to be applied by theantenna elements of the auxiliary antenna array to minimize (or at leastreduce) the power in the interference mitigated signal for each of adefined number of possible directions in which a main beam of theprimary antenna array may be steered. Additionally or alternatively, thepower in the interference signal may be measured continually and used asfeedback to continually adapt the complex weights applied by the antennaelements of the auxiliary antenna array substantially in real-time.

In some implementations, the desired signal may be transmitted bysatellites within a constellation of two or more satellites orbiting theearth. Therefore, the direction of a main beam of the primary antennaarray may be changed relatively frequently to account for changes in theposition of a particular satellite from which the desired signal isbeing received as the particular satellite orbits the earth. As the beamof the primary antenna array is steered in this manner, occasionally themain beam of the primary antenna array may be pointed substantially inthe direction of the signal being transmitted by the nearby wirelesscommunication terminal. When this occurs, the noise in the main signalcaused by the nearby wireless communication terminal may make itdifficult or impossible to extract the desired signal from the mainsignal. Therefore, when it is determined that pointing the main beam ofthe primary antenna array may subject the primary antenna array tosubstantial interference from a nearby wireless communication terminal,the main beam of the primary antenna array may be steered in a differentdirection that is favorable for receiving the desired signal fromanother one of the satellites in the satellite constellation.

With reference to FIG. 3, a block diagram of a wireless communicationterminal 300 configured to provide interference mitigation isillustrated in accordance with a non-limiting implementation of thepresent disclosure. A primary transmit/receive antenna array 310includes a number of antenna elements 312(a)-(m). The antenna elements312(a)-(m) collectively are configured to transmit and/or receivesignals. The primary transmit/receive antenna array 310 may besteerable, for example, to enable one or more main beams of the primarytransmit/receive antenna array 310 to be steered in directions that arefavorable for transmitting and/or receiving signals. For example, ifwireless communication terminal 300 is configured to communicate withone or more satellites, the primary transmit/receive antenna array 310may be steerable to train a main beam of the primary transmit/receiveantenna array 310 in directions favorable for communicating with atarget satellite. In some implementations, the antenna elements312(a)-(m) may include phase shifters that enable one or more main beamsof the primary transmit/receive antenna array 310 to be steered.

In some situations, when operating in a receive mode to receive adesired signal, the primary transmit/receive antenna array 310 mayreceive interfering signals in its side lobe(s). For example, if thewireless communication terminal 300 is located in close physicalproximity to another wireless communication terminal (not shown) thattransmits signals in a similar, adjacent, neighboring, and/oroverlapping frequency band to the frequency band in which the wirelesscommunication terminal 300 receives signals, the wireless communicationterminal 300 may receive signals transmitted by the other wirelesscommunication terminal in its side lobe(s). Although the gain in theside lobe(s) may be low relative to the gain in the main beam, if thepower of the interfering signal is high relative to the power of thesignal desired to be received, the interfering signal received in theside lobe(s) may degrade and/or interfere with the reception of thedesired signal.

An auxiliary receive antenna array 320 includes a number of auxiliaryantenna elements 322(a)-(n). In certain implementations, the number ofprimary antenna elements 312(a)-(m) in the primary transmit/receivearray 310 may be greater (even significantly greater) than the number ofauxiliary antenna elements 322(a)-(n) in the auxiliary receive antennaarray 320. The number of antenna elements in each antenna array 310 and320 may vary depending on the implementation taking into account factorssuch as, for example, cost, gain required, device form factor, etc.

The primary antenna elements 312(a)-(m) in the primary transmit/receiveantenna array 310 each may include an antenna 314(a)-(m) and atransmit/receive module 316(a)-(m). Each transmit/receive module316(a)-(m) may include one or more band pass filters (e.g. for filteringout frequencies outside of the frequency band(s) in which the wirelesscommunication terminal 300 is intended to receive signals), a low noiseamplifier (e.g., for amplifying received signals), a transmit poweramplifier (e.g., for amplifying signals to be transmitted),radio-frequency switches (e.g., for switching between transmit andreceive modes) and/or a phase shifter. The primary antenna elements312(a)-(m) of the primary transmit/receive antenna array 310 areconfigured to receive variants of a main signal (e.g., time and/or phaseshifted variants of the main signal). The outputs of the primary antennaelements 312(a)-(m) are combined by a radio frequency (RF) combiner 330.Each of these components in the primary transmit/receive antenna array310 may operate at RF.

BSC 340 is configured to steer a main beam of the primarytransmit/receive antenna array 310 in desired directions. For example,BSC 340 may control phase shifters included in the transmit/receivemodules 316(a)-316(m) to steer a main beam of the primarytransmit/receive antenna array 310.

The auxiliary antenna elements 322(a)-(n) in the auxiliary receiveantenna array 320 each may include an antenna 324(a)-(n) and a receivemodule 326(a)-326(n). Each receive module 326(a)-(n) may include one ormore filters (e.g., for filtering out frequencies outside of thefrequency bands in which the wireless communication terminal 300 isintended to receive signals), a low noise amplifier (e.g., foramplifying received signals), and a complex weight module for applyingcomplex weights to received signals (e.g., to shift the amplitude and/orphase of the received signals). The auxiliary antenna elements326(a)-326(n) of the auxiliary receive antenna array 320 are configuredto receive variants of a secondary signal (e.g., time and/or phaseshifted variants of the secondary signal). The outputs of the auxiliaryantenna elements 326(a)-326(n) are combined by an RF combiner 350.Similar to the components of the primary transmit/receive antenna array310, each of these components of the auxiliary receive antenna array 320may also operate at RF.

In certain implementations, the auxiliary receive antenna array 320 maybe configured to sample an interfering signal. For example, theauxiliary receive antenna array 320 may be configured to sample aninterfering signal transmitted by another wireless communicationterminal located in close physical proximity to wireless communicationterminal 300 that also may be received in the side lobe(s) of theprimary transmit/receive antenna array 310. In such cases, the output ofRF combiner 350, represents a model of the interfering signal receivedin the side lobe(s) of the primary transmit/receive antenna array 310and can be subtracted from the main signal received by the primarytransmit/receive antenna array 310 by RF combiner 330 to cancel ormitigate interference in the signal received by the primarytransmit/receive antenna array 310. This subtraction may occur at RF.The signal output from RF combiner 330 may be transmitted to modem 355for further processing by the wireless communication terminal 300. Insome implementations, the signal output from RF combiner 330 may beconverted to an intermediate frequency (e.g., a frequency lower than RFfrequencies) before being transmitted to modem 355.

In certain implementations, ICC 360 controls the complex weights appliedto the variants of the secondary signal received by the receive modules326(a)-326(n) of the auxiliary receive antenna array 320, for example,to minimize (or mitigate) the interference in the signal output by RFcombiner 330. The ICC 360 may adjust the complex weights according to analgorithm. For example, power receiver 370 may measure the power in thesignal output by RF combiner 330, and the algorithm may be configured toadjust the complex weights applied by the receive modules 326(a)-326(n)to minimize the power measured in the signal output by RF combiner 330.In certain implementations, the power receiver may be implemented as atuned power meter. Additionally or alternatively, the power receiver mayinclude a power detector that measures power in the bandwidth of thewireless communication terminal 300 at one or more frequencies to whichthe power detector is tuned.

In certain implementations, BSC 340 may be configured to steer a mainbeam of primary transmit/receive antenna array 310 to a predeterminednumber of different positions, and corresponding sets of complex weightsto be applied by the receive modules 326(a)-326(n) may be determined foreach of the predetermined positions of the main beam of primarytransmit/receive antenna array 310. These complex weights may bedetermined during a calibration process for wireless communicationterminal 300. The calibration process may be conducted while aninterfering signal is known to be present. For example, while anotherwireless communication terminal located in close physical proximity towireless communication terminal 300 is transmitting, BSC 340 may steer amain beam of primary transmit/receive antenna array 310 to each of thepredetermined different positions, and, for each position of the mainbeam of the primary transmit/receive antenna array 310, appropriatecomplex weights to be applied by receive modules 326(a)-326(n) may bedetermined to minimize the power in the signal output by RF combiner330. These complex weights then may be stored by ICC 360 (e.g., in atable or similar data structure). Then, when wireless communicationterminal 300 is operating in the receive mode, the BSC 340 maycommunicate an indication of the current position of a main beam of theprimary transmit/receive antenna array 310 to ICC 360, and ICC 360 mayset the appropriate complex weights to be applied by the receive modules326(a)-(n) based on the current position of the main beam of the primarytransmit/receive antenna array 310 as determined during the calibrationprocess.

Additionally or alternatively, ICC 360 continually may update theweights to be applied by receive modules 326(a)-(n) in an effort tocontinually minimize the power in the signal output by RF combiner 330as measured by power receiver 370. In such implementations, BSC 340 maybe configured to steer a main beam of primary transmit/receive antennaarray 310 to a predetermined number of different positions or,alternatively, the different positions to which BSC 340 can steer themain beam of primary transmit/receive antenna array 310 may not bepredetermined. For example, BSC 340 may continually adjust the phaseshifts to be applied by transmit/receive modules 312(a)-312(m) to steerthe main beam of primary transmit/receive antenna array 310 to differentpositions perceived as favorable for transmitting a signal to and/orreceiving a signal from one or more desired targets (e.g., satellitesorbiting the earth).

In some implementations, wireless communications terminal 300 may beconfigured to receive a desired signal from two or more satellitesorbiting the earth. In such implementations, primary transmit/receiveantenna array 310 may be configured to produce multiple different mainbeams, each of which may be steered independently from the other(s). Forexample, primary transmit/receive antenna array 310 may be configured toproduce a handoff beam and a traffic beam. The handoff beam continuallymay be scanned to identify and locate one or more satellites with whichthe wireless communication terminal 300 can communicate at a given time.If multiple satellites are available for communication with the wirelesscommunication terminal 300, a preferred satellite for the wirelesscommunication terminal 300 to communicate with may be determined basedon, for example, signals received from the different satellites in thehandoff beam. Meanwhile, the traffic beam may handle actual traffic(e.g., voice or data) and, when multiple satellites are available forwireless communication terminal 300 to communicate with, may be steeredto positions perceived as being favorable for communicating with thepreferred satellite. In such implementations, modem 355 may have twoinput ports, one for signals received in the handoff beam and the otherfor signals received in the traffic beam.

Furthermore, in some implementations, auxiliary receive antenna array320 also may be configured to produce multiple different main beams thatcan be steered independently of each other, for example, a handoff beamand a traffic beam. In such implementations, the signal received in thehandoff beam of auxiliary antenna array 320 may be used to mitigateinterference in the signal received in the handoff beam of the primarytransmit/receive antenna array 310 and the signal received in thetraffic beam of auxiliary receive antenna array 320 may be used tomitigate interference in the signal received in the traffic beam of theprimary transmit/receive antenna array 310, for example, according tothe interference mitigation techniques described herein (e.g., bycoordinating the steering of the beams of the primary transmit/receiveantenna array 310 and the auxiliary receive antenna array 320.

In certain scenarios, steering a main beam of primary transmit/receiveantenna array 310 to track a particular satellite may result in steeringthe main beam of primary transmit/receive antenna array 310 in adirection that causes the interfering signal to be received in the mainbeam of primary transmit/receive antenna array 310. In such scenarios,the auxiliary receive antenna array 320 may not be effective inmitigating interference in the primary transmit/receive antenna array310. Thus, if wireless communication terminal 300 determines thatsteering a main beam of primary transmit/receive antenna array 310 totrack a particular satellite will result in the interfering signal beingreceived in the main beam of primary transmit/receive antenna array 310,wireless communication terminal 300 instead may steer the main beam ofprimary transmit/receive antenna array 310 to initiate communicationswith a different satellite.

In certain alternative implementations, the model of the interferingsignal may be subtracted from the main signal at an intermediatefrequency (e.g., a frequency that is lower than RF frequencies) insteadof at RF. For example, in such implementations, the transmit/receivemodules 316(a)-(m) may include circuitry (e.g., including a localoscillator) that converts the variants of the main signal received at RFto an intermediate frequency. After converting the variants of the mainsignal to the intermediate frequency, the transmit/receive modules316(a)-(m) also may filter (e.g., using a bandpass filter) and/oramplify (e.g., using a low noise amplifier) the received signals. Theintermediate frequency signals output by the transmit/receive modules316(a)-(m) then may be transmitted to combiner 330 where they arecombined at the intermediate frequency instead of at RF. Alternatively,in some implementations, the signals output by transmit/receive modules316(a)-(m) may be output at RF and combined into an RF main signal thatis converted to the intermediate frequency before being transmitted tocombiner 330. The receive modules 326(a)-326(n) of the auxiliary receiveantenna array 320 also may convert the variants of the secondary signalthat they receive from RF to the intermediate frequency before thesignals are combined by combiner 350. The resulting intermediatefrequency model of the interfering signal then may be subtracted fromthe intermediate frequency main signal by combiner 330. Alternatively,the variants of the secondary signal received by antenna elements324(a)-(n) may be combined at RF by combiner 350, and the combinedsignal then may be converted to the intermediate frequency before beingsubtracted from the main signal by combiner 330. In such alternativeimplementations, the complex weights applied to the variants of thesecondary signal by the receive modules 326(a)-(n) may be determined tominimize the power measured in the signal that results from subtractingthe intermediate frequency model of the interfering signal from theintermediate frequency main signal.

In still other alternative implementations, the variants of the mainsignal received by the primary antenna elements 312(a)-(m) may beconverted to digital baseband before being combined. Similarly, themodel of the interfering signal received in the side lobe(s) of theprimary transmit/receive antenna array 310 also may be converted todigital baseband before being subtracted from the main signal. Forexample, in such implementations, the signals output by transmit/receivemodules 316(a)-(m) (e.g., at RF or an intermediate frequency) may beconverted to digital baseband (e.g., by modems or demodulators) beforebeing combined into a digital baseband main signal. Alternatively, thesignals output by transmit/receive modules 316(a)-(m) may be combined togenerate a main signal (e.g., an RF or intermediate frequency mainsignal) that then is converted to a digital baseband main signal (e.g.,by a modem or a demodulator). Similarly, the signals output by receivemodules 326(a)-326(n) (e.g., at RF or an intermediate frequency) may beconverted to digital baseband (e.g., by modems or demodulators) beforebeing combined to generate a digital baseband model of the interferingsignal that then may be subtracted from the digital baseband mainsignal. Alternatively, the signals output by receive modules 326(a)-(n)may be combined by combiner 350 to generate a model of the interferingsignal that then is converted to digital baseband (e.g., by a modem ordemodulator) and subtracted from the digital baseband main signal. Insuch alternative implementations, the complex weights applied to thevariants of the secondary signal by the receive modules 326(a)-(n) maybe determined to minimize the power measured in the signal that resultsfrom subtracting the digital baseband model of the interfering signalfrom the digital baseband main signal.

Application of the teachings of the present disclosure may enable thesimultaneous operation of two or more wireless communication terminalslocated in close physical proximity to one another even if the wirelesscommunication terminals transmit and/or receive using similar, adjacent,neighboring, and/or overlapping frequencies. For example, application ofthe teachings of the present disclosure may enable an IRIDIUM® satellitecommunication terminal to be operated in the presence of a nearby activeINMARSAT® satellite communication terminal.

Aspects of the present disclosure may be implemented entirely inhardware, entirely in software (including firmware, resident software,micro-code, etc.) or in combinations of software and hardware that mayall generally be referred to herein as a “circuit,” “module,”“component,” or “system.” Furthermore, aspects of the present disclosuremay take the form of a computer program product embodied in one or morecomputer-readable media having computer-readable program code embodiedthereon.

Any combination of one or more computer-readable media may be utilized.The computer-readable media may be a computer-readable signal medium ora computer-readable storage medium. A computer-readable storage mediummay be, for example, but not limited to, an electronic, magnetic,optical, electromagnetic, or semiconductor system, apparatus, or device,or any suitable combination of the foregoing. More specific examples (anon-exhaustive list) of such a computer-readable storage medium includethe following: a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), an appropriate optical fiberwith a repeater, a portable compact disc read-only memory (CD-ROM), anoptical storage device, a magnetic storage device, or any suitablecombination of the foregoing. In the context of this document, acomputer-readable storage medium may be any tangible medium that cancontain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer-readable signal medium may include a propagated data signalwith computer-readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer-readable signal medium may be any computer-readable medium thatis not a computer-readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device. Program codeembodied on a computer-readable signal medium may be transmitted usingany appropriate medium, including but not limited to wireless, wireline,optical fiber cable, RF signals, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including object oriented programming languages,dynamic programming languages, and/or procedural programming languages.

The flowchart and block diagrams in the figures illustrate examples ofthe architecture, functionality, and operation of possibleimplementations of systems, methods and computer program productsaccording to various aspects of the present disclosure. In this regard,each block in the flowchart or block diagrams may represent a module,segment, or portion of code, which comprises one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that, in some alternative implementations, thefunctions noted in the block may occur out of the order illustrated inthe figures. For example, two blocks shown in succession may, in fact,be executed substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. It will also be noted that each block of the block diagramsand/or flowchart illustration, and combinations of blocks in the blockdiagrams and/or flowchart illustration, can be implemented by specialpurpose hardware-based systems that perform the specified functions oracts, or combinations of special purpose hardware and computerinstructions.

The interference mitigation techniques described herein may be employedin a wide variety of different contexts to enable concurrent operationof two or more co-located wireless communication terminals. For example,the interference mitigation techniques described herein may be employedto enable concurrent operation of two satellite communication terminalsmounted within a short distance of one another on a ship or aircraft.Similarly, the interference mitigation techniques described herein maybe employed to enable concurrent operation of two terminals (e.g.,transceivers) on a single satellite.

The terminology used herein is for the purpose of describing particularaspects only and is not intended to be limiting of the disclosure. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of anymeans or step plus function elements in the claims below are intended toinclude any disclosed structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present disclosure has been presentedfor purposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of thedisclosure. The aspects of the disclosure herein were chosen anddescribed in order to explain the principles of the disclosure and thepractical application, and to enable others of ordinary skill in the artto understand the disclosure with various modifications as are suited tothe particular use contemplated.

What is claimed is:
 1. A wireless communication terminal comprising: aprimary antenna array including a first number of primary antennaelements; a first controller configured to steer a main beam of theprimary antenna array in a desired direction; an auxiliary antenna arrayincluding a second number of auxiliary antenna elements; a secondcontroller configured to control, based on the desired direction of themain beam of the primary antenna array, complex weights to be applied byat least some of the auxiliary antenna elements; and at least one signalcombiner configured to: combine signals received from auxiliary antennaelements into an interfering signal, the interfering signal to modelinterference from a co-located wireless communication terminal receivedin a side lobe of the primary antenna array when the main beam is in thedesired direction, and subtract the interfering signal from signalsreceived from primary antenna elements to produce an interferencemitigated signal.
 2. The wireless communication terminal of claim 1,further comprising a power receiver to measure power of the interferencemitigated signal, wherein the second controller is configured to controlthe complex weights to be applied to reduce the power of theinterference mitigated signal measured by the power receiver.
 3. Thewireless communication terminal of claim 1, further comprising: anoscillator configured to convert the interference mitigated signal to anintermediate frequency, wherein the interfering signal is subtractedfrom the signals received from the primary antenna elements before theinterference mitigated signal is converted to the intermediatefrequency.
 4. The wireless communication terminal of claim 1, wherein:the first controller is configured to steer the main beam of the primaryantenna array in a plurality of predetermined directions; and the secondcontroller is further configured to control the complex weights to beapplied by the at least some of the auxiliary antenna elements for eachpredetermined direction in which the first controller is configured tosteer the main beam of the primary antenna array.
 5. The wirelesscommunication terminal of claim 1, wherein the at least one signalcombiner includes: a first signal combiner configured to combine thesignals received from the auxiliary antenna elements into theinterfering signal; and a second signal combiner that is different fromthe first signal combiner configured to subtract the interfering signalfrom the signals received from the primary antenna elements to producethe interference mitigated signal.
 6. The wireless communicationterminal of claim 1, wherein the at least one signal combiner includes:a first signal combiner to combine signals received from primary antennaelements into a main signal; a second signal combiner that is differentfrom the first signal combiner configured to combine signals receivedfrom the auxiliary antenna elements into the interfering signal; and athird signal combiner that is different from the first and second signalcombiners configured to subtract the interfering signal from the mainsignal to produce the interference mitigated signal.
 7. The wirelesscommunication terminal of claim 1, wherein the at least one signalcombiner is configured to: combine signals received from all of theauxiliary antenna elements into the interfering signal; and subtract theinterfering signal from signals received from all of the primary antennaelements to produce an interference mitigated signal.
 8. The wirelesscommunication terminal of claim 1, wherein: the first controller isconfigured to: steer the main beam of the primary antenna in a newdesired direction, and communicate an indication of the new desireddirection to the second controller; and the second controller isconfigured to: receive the indication of the new desired direction, andchange the complex weights to be applied by at least some of theauxiliary antenna elements based on the new desired direction.
 9. Thewireless communication terminal of claim 1, wherein: each of at leastsome of the primary antenna elements is configured to apply a complexweight to a signal received by the primary antenna element; and thefirst controller is configured to steer the main beam of the primaryantenna array in a desired direction by controlling complex weightsapplied by the at least some primary antenna elements to the signalsreceived by the at least some primary antenna elements.
 10. The wirelesscommunication terminal of claim 9, wherein each of at least some of theprimary antenna elements include: a power amplifier to amplify signalsto be transmitted by the primary antenna element; and a low noiseamplifier to amplify signals received by the primary antenna element.11. The wireless communication terminal of claim 1, wherein the firstnumber of primary antenna elements is greater than the second number ofauxiliary antenna elements.
 12. The wireless communication terminal ofclaim 1, wherein the second controller is configured to control, basedon the desired direction of the main beam of the primary antenna array,a complex weight to be applied by each auxiliary antenna element. 13.The wireless communication terminal of claim 1, wherein: a desiredsignal is transmitted by two or more satellites orbiting the earth; andthe first controller is configured to: steer the main beam of theprimary antenna array in a desired direction to receive the desiredsignal from a first one of the satellites, and change the direction ofthe main beam of the primary antenna array to a new desired direction toreceive the desired signal from a second one of the satellites based ona determination that the main beam of the primary antenna array will besubjected to interference from a co-located satellite terminal whensteered in the desired direction to receive the desired signal from thefirst satellite.
 14. A method for processing a desired signal by awireless communication terminal, comprising: receiving a main signalwith a primary antenna array, the main signal including noise from aproximally located wireless communication terminal received in one ormore side lobes of the primary antenna array; setting complex weights tobe applied by individual antenna elements of the auxiliary antenna arraybased on a direction of a main beam of the primary antenna array;applying the complex weights to shift signals received by the individualantenna elements; combining the shifted signals received by theindividual antenna elements into an interfering signal to model thenoise from the proximally located wireless communication terminalreceived in the one or more side lobes of the primary antenna array; andsubtracting the interfering signal from the main signal to produce aninterference mitigated signal.
 15. The method of claim 14, whereinsetting the complex weights comprises: measuring power in theinterference mitigated signal; and setting the complex weights to reducethe power measured in the interference signal.
 16. The method of claim14, further comprising steering the main beam of the primary antennaarray to a particular one of a plurality of predetermined directions,wherein setting the complex weights includes setting the complex weightsbased on the main beam of the primary antenna having been steered in theparticular direction.
 17. The method of claim 14, wherein receiving amain signal with a primary antenna array comprises: receiving variantsof the main signal with corresponding antenna elements of the primaryantenna array; and combining variants of the main signal received fromprimary antenna elements to produce the main signal.
 18. The method ofclaim 14, further comprising: steering the main beam of the primaryantenna array in a new direction; and setting new complex weights to beapplied by individual antenna elements of the auxiliary antenna arraybased on the main beam being steered in the new direction.
 19. Themethod of claim 14, wherein: receiving a main signal with a primaryantenna array includes receiving a main signal that includes a desiredsignal transmitted by a first satellite orbiting the earth; and themethod further comprises: determining that steering the main beam of theprimary antenna array in a new direction to continue to receive thedesired signal from the first satellite will subject the main beam ofthe primary antenna array to interference from a co-located satelliteterminal, and steering the main beam of the primary antenna array in adifferent direction to receive the desired signal from a secondsatellite orbiting the earth that is different from the first satellite.20. A satellite communication terminal comprising: a primary antennaarray including a first number of primary antenna elements; a firstcontroller configured to steer a main beam of the primary antenna arrayin a desired direction to receive a desired signal from a satelliteorbiting the earth; an auxiliary antenna array including a second numberof auxiliary antenna elements; a second controller configured to controlcomplex weights to be applied by at least some of the auxiliary antennaelements; and at least one signal combiner configured to: combinesignals received from auxiliary antenna elements into an interferingsignal, the interfering signal to model a signal transmitted by aco-located satellite communication terminal received in one or more sidelobes of the primary antenna array when the main beam is in the desireddirection, and subtract the interfering signal from signals receivedfrom primary antenna elements to produce an interference mitigatedversion of the desired signal.